1. Field of the Invention
The invention relates to a hue adjusting device and, more particularly, to a hue adjusting device which can adjust different hues within the color axis by different rotation angles.
2. Description of the Prior Art
When looking at an image, users often adjust some colors of the image based on their preference. For example, a user may try to make the sky bluer or the grasslands greener in an image. In general, the adjustable parameters in the image comprise lightness, hue, and saturation. However, for most of the applications, it is more suitable to use the hue to divide colors.
In order to deal with the color of an image, the signal of the image must be converted from the original color space (e.g. RGB) to the color space (e.g. YCbCr, YUV, CIELab, etc.) where the lightness (Y) and the colors (C) are separated. Then, the information about the lightness, the hue, and the saturation of the image can be obtained. Referring to FIG. 1, FIG. 1 is a schematic diagram of Lab color space. Taking Lab color space for example, L represents lightness component; a and b represent color components. As shown in FIG. 1, the lightness (L) is controlled by the height, the hue (H) is controlled by the angle, and the saturation (S) is controlled by the radius.
The distribution of the hue ranges from 0° to 360° in the Y/C separated color space. The distribution of the hue can be divided into several color axes with different range of angles based on the practical requirement. Referring to FIG. 2, FIG. 2 is a schematic diagram of dividing the hue into six color axes in the prior art. In the prior art, the conventional integrated circuit (IC) used to adjust colors often divides colors into six color axes according to the hues. As shown in FIG. 2, these color axes are red (R), blue (B), green (G), cyan (C), magenta (M), and yellow (Y) respectively. Furthermore, the color of skin may be added to those color axes by some ICs. It is convenient for the user to adjust when there are seven color axes.
Referring to FIG. 3, FIG. 3 is a schematic diagram of selecting color axis and adjusting the state of image. As shown in FIG. 3, a user can use on screen display (OSD) to select the axis which is desired to be adjusted first, and then he/she can select the state of image which is desired to be adjusted (e.g. lightness, hue, or saturation).
In general, the hue of certain pixel in an image signal can be adjusted by changing its hue angle. When adjusting the hue of certain color axis in an image, all hues in the color axis are rotated to the same angle based on the prior art. As a result, it causes difference and uneven lines. In other words, even though all colors are in the same axis, the rotation angles of hue are supposed to be different.
Therefore, the main scope of the invention is to provide a hue adjusting device to solve the above mentioned problems.